Valve element and method for manufacturing the valve element

Abstract

To provide a technique for compatibly downsizing a valve device to be driven using electrostatic attraction and reducing power consumption in simple manufacturing steps.SOLUTION: A valve device for controlling the distribution of fluid includes a first movable electrode part including a fluid introduction port where the fluid is distributed, a second movable electrode part having a discharge port for the fluid to be discharged therefrom and arranged at a space from the first movable electrode part while covering the fluid introduction port, a spacer part for securing a space between the first movable electrode part and the second movable electrode part, and a frame part forming a back chamber communicated with the fluid introduction port and supporting the first movable electrode part. Electrostatic attraction caused by applying voltage to the first movable electrode part and the second movable electrode part is used for attracting the first movable electrode part and the second movable electrode part to each other to seal the fluid introduction port.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a valve element and a method for manufacturing the valve element. [Background technology]

[0002] A valve element for controlling the flow of fluid has been known in the past, which has two electrode parts arranged opposite each other, and has a structure in which an electrostatic attraction is generated by applying a voltage to each electrode of the two electrode parts, and a fluid inlet provided in one electrode part is sealed by the other electrode part (for example, Patent Document 1). Figure 1 shows a schematic diagram of a valve element 9 having such a structure.

[0003] FIG. 1A is a schematic cross-sectional view of valve element 9 when the valve is in the "open" state, and FIG. 1B is a schematic cross-sectional view of valve element 9 when the valve is in the "closed" state. As shown in FIG. 1, valve element 9 is configured so that fluid is introduced through a fluid inlet 92 provided in a substrate 91 (fixed electrode) and the fluid is discharged through an outlet (not shown) provided in a diaphragm 93 (movable electrode) that is formed to be movable relative to the substrate 91. When an electrostatic attraction is generated by applying a voltage between the substrate 91 (fixed electrode) and the diaphragm 93 (movable electrode), the attractive force attracts the diaphragm 93 to the substrate 91, allowing the diaphragm 93 to seal the fluid inlet 92. In this way, the flow rate of the fluid can be controlled by blocking the flow of the fluid or adjusting the distance between the diaphragm 93 and the substrate 91 by adjusting the applied voltage.

[0004] In this case, the electrostatic attraction can be expressed by the following equation (1):

number

[0005] In the above formula (1), F is the electrostatic attractive force, ε is the dielectric constant of air, S is the area where the two electrodes face each other, V is the applied voltage, and d is the distance between the two electrodes. In other words, the electrostatic attractive force F is highly dependent on the applied voltage V and the distance d between the electrodes, and lowering the applied voltage V or widening the distance d between the electrodes significantly weakens the electrostatic attractive force F, resulting in a decrease in the driving force that drives the valve (i.e., that pulls the diaphragm 93 toward the substrate 91).

[0006] On the other hand, from the viewpoint of the fluid discharge characteristics, the greater the distance between the two electrodes and the larger the area of ​​the fluid inlet 92 and outlet (i.e., the smaller the opposing area between the two electrodes), the more efficiently the fluid can be discharged.

[0007] As described above, conventionally known valves driven by electrostatic attraction require a certain distance between the electrodes to ensure good fluid discharge characteristics when the valve is in the "open" state. This means that in order to obtain a sufficient electrostatic attraction force F to drive the valve, adjustments must be made by increasing the electrode area S or the applied voltage V. In other words, it has been difficult to achieve both good fluid discharge characteristics and miniaturization of the valve element and low power consumption.

[0008] On the other hand, in a normally closed microvalve formed by bonding two semiconductor substrates, a technique has been proposed in which the valve is opened by bending the two semiconductor substrates in opposite directions using a thermal actuation method using a bimetal (for example, Patent Document 2). The step allows the distance between the valve port and the valve body to be greater than when only one of the substrates is deflected, and good fluid discharge characteristics can be obtained with low power consumption. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 63-307959 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-266224 Summary of the Invention [Problem to be solved by the invention]

[0010] However, in the microvalve disclosed in Patent Document 2, electrodes for driving the valve are provided on the top and bottom (front and back) of the valve element, requiring wiring to be run on both the top and bottom of the valve element. Furthermore, the microvalve is manufactured by bonding two substrates together, and precise wafer alignment is required to properly bond them. In other words, the manufacturing process for the microvalve described in Patent Document 2 is complicated, making it difficult to manufacture.

[0011] The present invention has been made in consideration of the above problems, and aims to provide a technology that can achieve both miniaturization and low power consumption of a valve element that is driven using electrostatic attraction through a simple manufacturing process. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention employs the following configuration: A valve element for controlling the flow of a fluid, comprising: a first movable electrode portion having a fluid inlet through which the fluid flows; a second movable electrode portion having an outlet through which the fluid is discharged, the second movable electrode portion being disposed on one surface side of the first movable electrode portion so as to cover the fluid inlet port and spaced apart from the first movable electrode portion; a spacer portion that ensures the gap between the first movable electrode portion and the second movable electrode portion; a frame portion that forms a back chamber that communicates with the fluid inlet on the other surface side of the first movable electrode portion and supports the first movable electrode portion, This valve element is characterized in that it is configured to be able to seal the fluid inlet by attracting the first movable electrode portion and the second movable electrode portion together using electrostatic attraction generated by applying a voltage to the first movable electrode portion and the second movable electrode portion.

[0013] As described above, the valve port (fluid inlet of the first movable electrode portion) and the structure sealing it (second movable electrode portion) are configured to be attracted to each other by electrostatic attraction, which allows the approach distance between the two electrodes to be greater when the same voltage is applied, compared to when one side is a fixed electrode. This allows the distance between the two electrodes when the valve is in the "open" state to be greater without changing the applied voltage, compared to when one side is a fixed electrode.

[0014] In this way, good fluid discharge characteristics can be obtained, and the voltage applied when closing the valve can be reduced without increasing the electrode area, making it possible to achieve a smaller valve element with lower power consumption. Furthermore, with the above configuration, each component can be manufactured by stacking thin films on a single semiconductor substrate, making it easy to manufacture using semiconductor manufacturing processes.

[0015] The valve element may have a plurality of pairs of the fluid inlet and the corresponding outlet, and the pairs of the fluid inlet and the corresponding outlet may be arranged in an array.

[0016] This configuration can further improve the fluid discharge characteristics when the valve is "open," and can provide good fluid discharge characteristics even when the distance between the electrodes is reduced, thereby enabling the valve element to be made smaller.

[0017] The present invention also provides a method for manufacturing a valve element for controlling fluid flow, comprising: a first electrode forming step of forming a first movable electrode film on a semiconductor substrate, the first movable electrode film having a first movable electrode and a fluid inlet through which the fluid flows; a sacrificial layer film forming step of forming a sacrificial layer film on the first movable electrode film and the semiconductor substrate using an insulating material; a second electrode film forming step of forming a second movable electrode film on the sacrificial layer film, the second movable electrode film having a second movable electrode and an outlet through which the fluid is discharged; a connection electrode forming step of forming a first connection electrode connected to the first movable electrode and a second connection electrode connected to the second movable electrode; a back chamber forming step of forming a back chamber in the semiconductor substrate; a sacrificial layer film etching step of etching the sacrificial layer film while leaving a spacer portion that ensures a gap between the first movable electrode film and the second movable electrode film, The present invention can also be understood as a method for manufacturing a valve element characterized by the above-mentioned.

[0018] The present invention can be achieved by combining the above-described configurations together as long as no technical contradiction occurs. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a technology that can achieve both miniaturization and low power consumption of a valve element that is driven using electrostatic attraction through a simple manufacturing process. [Brief explanation of the drawings]

[0020] [Figure 1] Figure 1A is a first diagram showing a schematic diagram of a valve element of a conventionally known type that drives a valve by electrostatic attraction. Figure 1A is a second diagram showing a schematic diagram of a valve element of a conventionally known type that drives a valve by electrostatic attraction. [Figure 2] Fig. 2A is a plan view showing an outline of a valve element according to Example 1 of the present invention. Fig. 2B is a first diagram showing an outline of a cross section of the valve element according to Example 1 of the present invention. Fig. 2C is a diagram explaining details of an inlet and an outlet according to Example 1 of the present invention. [Figure 3]Figure 3A is a first diagram showing a manufacturing process for a valve element according to Example 1 of the present invention. Figure 3B is a second diagram showing a manufacturing process for a valve element according to Example 1 of the present invention. Figure 3C is a third diagram showing a manufacturing process for a valve element according to Example 1 of the present invention. Figure 3D is a fourth diagram showing a manufacturing process for a valve element according to Example 1 of the present invention. Figure 3E is a fifth diagram showing a manufacturing process for a valve element according to Example 1 of the present invention. Figure 3F is a sixth diagram showing a manufacturing process for a valve element according to Example 1 of the present invention. [Figure 4] 4A is a first view showing a modified example of the valve element of Example 1. FIG. 4B is a second view showing a modified example of the valve element of Example 1. [Figure 5] Figure 5A is a third diagram showing a modified example of the valve element of Example 1. Figure 5B is a fourth diagram showing a modified example of the valve element of Example 1. [Figure 6] Figure 6A is a fifth diagram showing a modified example of the valve element of Example 1. Figure 6B is a sixth diagram showing a modified example of the valve element of Example 1. Figure 6C is a seventh diagram showing a modified example of the valve element of Example 1. Figure 6D is an eighth diagram showing a modified example of the valve element of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0021] <Application example> An outline of an application example of the present invention will be explained below with reference to some of the drawings. The present invention is directed to a microelectromechanical system (MEMS) manufactured by a semiconductor manufacturing process, for example. This valve can be applied as a valve element 1 of a valve for a valve system (Valve for a Mechanical System). Fig. 2 is a diagram showing an outline of the valve element 1 according to this application example, and Fig. 2A is a plan view showing an outline of the valve element 1 according to this application example. Fig. 2B is a schematic cross-sectional view showing the cross section AA of the valve element 1 in Fig. 2A when the valve is in the "open" state, but both ends of the cross section are omitted. Fig. 2C is an enlarged view of the area surrounded by the dashed line in Fig. 2A, and is a diagram for explaining the shape and arrangement of an inlet 111 and an outlet 121, which will be described later.

[0022] The valve element 1 generally comprises a frame portion 13 made of a semiconductor, and a first movable electrode portion 11 and a second movable electrode portion 12 formed on the frame portion 13. The first movable electrode portion 11 and the second movable electrode portion 12 are both formed as flexible thin films, insulated by a spacer portion 14, and arranged at a predetermined interval.

[0023] The frame portion 13 is composed of a semiconductor substrate or the like, and has a back chamber 131 that serves as a flow path for the fluid flowing into the valve. The first movable electrode portion 11 is provided with a plurality of inlets 111 for introducing the fluid, and the second movable electrode portion 12 is provided with a plurality of outlets 121 for discharging the fluid. Note that the inlets 111 and outlets 121 are shown schematically in Figure 2A, and their specific shapes and positional relationship will be described in detail later.

[0024] 2B, when the valve is in the "open" state, a hollow portion 15 is formed between the second movable electrode portion 12 and the first movable electrode portion 11. When the valve is in the "open" state, the fluid can be introduced through the inlet 111 provided in the first movable electrode portion 11 and discharged through the outlet 121 provided in the second movable electrode portion 12, thereby allowing the fluid to circulate.

[0025] The valve element 1 according to this application example can open and close the valve by a so-called electrostatic drive system to control the flow of fluid (control of the flow rate, including blocking the flow). Specifically, by applying a voltage to the electrode 110 of the first movable electrode portion 11 and the electrode 120 of the second movable electrode portion 12, an electrostatic attraction is generated between the two electrodes, which attracts the second movable electrode portion 12 and the first movable electrode portion 11 toward each other, thereby reducing the gap between the second movable electrode portion 12 and the first movable electrode portion 11 (i.e., the volume of the hollow portion 15). The flow rate of the fluid can be controlled by changing the size of this gap. Furthermore, when the second movable electrode portion 12 and the first movable electrode portion 11 are completely in close contact with each other, the inlet 111 and the outlet 121 are positioned so that they do not overlap with each other, so the valve can be in the "closed" state, i.e., the flow of the fluid can be blocked.

[0026] In the valve element 1 according to this application example, the first movable electrode portion 11 and the second movable electrode portion 12 are both movable members formed in a thin film, so they will attract each other when electrostatic attraction occurs. Therefore, compared to conventional valve elements in which one electrode is configured as a fixed electrode, the distance between the electrodes can be made larger, resulting in good fluid discharge characteristics. In addition, it is possible to put the valve into the "closed" state with a small applied voltage.

[0027] Example 1 The following describes in more detail the mode for carrying out the present invention based on examples, with reference to the drawings (including the drawings already explained in the application examples above). However, unless otherwise specified, the specific configurations described in the examples are not intended to limit the scope of the present invention to those specific configurations.

[0028] (Valve element configuration) The valve element 1 according to this embodiment can be used, for example, as a MEMS valve for supplying and discharging gas to the cuff of a blood pressure monitor, and as shown in FIGS. 2A, 2B, and 2C, is generally configured to include a frame portion 13, a first movable electrode portion 11, and a second movable electrode portion 12. Since the valve element 1 has the same configuration as that of the valve element 1 described in the application example, detailed description of the contents described in the application example will be omitted. Furthermore, in this specification, the same components will be described using the same reference numerals.

[0029] The frame portion 13 is a hard substrate made of a semiconductor such as Si, and is provided with a back chamber 131 which serves as a flow path for the fluid flowing into the valve.

[0030] The first movable electrode portion 11 is a thin-film electrode member including a first movable electrode 110 made of, for example, Si, and is disposed across the upper surface side (the side shown in FIG. 2A , the same applies below) of the frame portion 13. The first movable electrode portion 11 is provided with an insulating film (for example, a SiN film) 112, which insulates it from the frame portion 13. The first movable electrode 110 is connected to an electrode pad 113, and is electrically connected to an external power source via the electrode pad 113 so that a voltage can be applied. The first movable electrode portion 11 is also provided with a plurality of inlets 111 for introducing fluid into the valve. The arrangement and shape of the inlets 111 will be described later.

[0031] The second movable electrode portion 12 is a flexible thin-film electrode member formed by covering a second movable electrode 120 made of, for example, Si with an insulating film (e.g., a SiN film) 122, and is provided with a plurality of exhaust ports 121. The arrangement and shape of the exhaust ports 121 will be described later. In this embodiment, the second movable electrode portion 12 is substantially circular in plan view, with a plurality of protrusions 124 arranged on the circumference. The protrusions 124 on the circumference are spaced a predetermined distance from the upper surface of the first movable electrode portion 11 by spacer portions 14 made of an insulator, and are arranged insulated from the first movable electrode portion 11. The spacer portions 14 may be made of, for example, silicon dioxide (SiO2), or may be made of, for example, phosphorus silicon glass (PSG), boron phosphorus silicon glass (BPSG), or the like. The second movable electrode 120 is connected to electrode pads 123, and is electrically connected to an external power source via the electrode pads 123, allowing a voltage to be applied thereto.

[0032] When a voltage is applied to both the second movable electrode 120 and the first movable electrode 110, an electrostatic attractive force is generated, attracting the second movable electrode portion 12 and the first movable electrode portion 11 to each other, and when they are in complete contact with each other, the inlet 111 is sealed by the second movable electrode portion 12, and the valve is in the "closed" state. Note that the explanation of driving the valve by the electrostatic attractive force method has been given above, so further explanation will be omitted.

[0033] Next, the inlet 111 of the first movable electrode portion 11 and the outlet 121 of the second movable electrode portion 12 will be described. FIG. 2C is an enlarged view of the area surrounded by the dashed line in FIG. 2A, showing the relative positions of the inlet 111 and the outlet 121. Note that the inlet 111 shown by the dashed line in FIG. 2C is not actually visible in a plan view of the valve element 1, but is shown merely to help understand its shape and relative positions. As shown in FIG. 2C, the inlet 111 and the outlet 121 form a pair in a positional relationship in which multiple outlets 121 surround one inlet 111 in a plan view. Specifically, elliptical outlets 121 are provided at positions corresponding to each side of a hexagon surrounding the circular inlet 111. As shown in FIG. 2A, the valve element 1 is configured such that many pairs of inlet 111 and outlet 121 are arranged in an array in a so-called honeycomb structure.

[0034] In this way, by configuring a large number of pairs of inlet ports 111 and outlet ports 121 to be arranged in an array, it is possible to reduce the flow path resistance of the fluid, and the fluid can be efficiently discharged even if the gap between the first movable electrode portion 11 and the second movable electrode portion 12 is small. This also makes it possible to reduce the voltage applied to electrostatically drive both electrode portions.

[0035] (Manufacturing method of valve element) Next, an example of a method for manufacturing the valve element 1 according to this embodiment will be described with reference to Figures 3A to 3F. Note that each of Figures 3A to 3F is a conceptual schematic cross-sectional view for the convenience of explaining the manufacturing process, and does not represent an accurate cross-sectional view of any part of the valve element 1. The valve element 1 can be manufactured by forming a thin film on a semiconductor substrate using a so-called semiconductor manufacturing process.

[0036] In the manufacturing flow of the valve element 1, first, a first movable electrode film that will become the first movable electrode portion 11, which includes a first movable electrode 110 and an inlet 111, is formed on a silicon substrate that constitutes the frame portion 13. This process corresponds to the first electrode formation step according to the present invention, and Fig. 3A is a schematic cross-sectional view showing the state after this process.

[0037] Next, a sacrificial layer film made of an insulating material is formed on the first movable electrode film and the semiconductor substrate, which will later become the spacer portion 14. This process corresponds to the sacrificial layer film formation step according to the present invention, and Fig. 3B is a schematic cross-sectional view showing the state after this process.

[0038] Subsequently, a second movable electrode film is formed on the sacrificial layer film to become the second movable electrode portion 12 including the second movable electrode 120 and the outlet 121. This process corresponds to the second electrode film forming step according to the present invention, and Fig. 3C is a schematic cross-sectional view showing the state after this process.

[0039] Next, an electrode pad 113 is formed to be connected to the first movable electrode 110, and an electrode pad 123 is formed to be connected to the second movable electrode 120. This process corresponds to the connecting electrode forming step according to the present invention, and Fig. 3D is a schematic cross-sectional view showing the state after this process.

[0040] Furthermore, a back chamber 131 is formed in the frame portion 13. This process corresponds to the back chamber forming step according to the present invention, and FIG. 3E is a schematic cross-sectional view showing the state after this process. Next, the sacrificial layer film is etched, leaving spacer portions 14 that ensure the gap between the first movable electrode portion 11 and the second movable electrode portion 12. This process corresponds to the sacrificial layer film etching step according to the present invention, and FIG. 3F is a schematic cross-sectional view showing the state after this process.

[0041] The valve element 1 according to this embodiment can be easily manufactured by laminating thin films on a single semiconductor substrate using the process described above. Furthermore, the valve element 1 according to this embodiment can obtain good fluid discharge characteristics without increasing the electrode area or the applied voltage. In other words, it is possible to easily manufacture a valve element that has good fluid discharge characteristics, is compact, and consumes less power.

[0042] (Modification of the support structure of the second movable electrode portion) In the above embodiment, the second movable electrode portion 12 is configured to be supported by the spacer portions 14 provided on the four protrusions 124. However, the support structure of the second movable electrode portion 12 is not limited to this. FIGS. 4A, 4B, 5A, and 5B are diagrams showing other examples of the support structure of the second movable electrode portion 12. The second movable electrode portion 12 may be configured to be supported by the spacer portions 14 provided on three protrusions 124 as shown in FIG. 4A, or may be configured to be supported by the spacer portions 14 provided on six protrusions 124 as shown in FIG. 4B. Furthermore, the second movable electrode portion 12 may be configured to be supported by the spacer portions 14 provided on eight protrusions 124 as shown in FIG. 5A, or may be configured to be supported by the spacer portions 14 provided around the entire circumference of a circle without providing any protrusions.

[0043] (Modifications of inlet and outlet) In the above embodiment, the shape and arrangement of the inlet 111 and the outlet 121 are circular. In the above embodiment, elliptical outlets 121 are provided at positions corresponding to the sides of a hexagon surrounding inlet 111, but various modifications are possible. Figures 6A, 6B, 6C, and 6D are diagrams showing other configurations of inlet 111 and outlet 121, respectively.

[0044] The shape and arrangement of the inlet 111 and the outlet 121 may be such that smaller circular outlets 121 are provided around the outer periphery of the circular inlet 111, as shown in FIG. 6A . Alternatively, the shape and arrangement of the inlet 111 and the outlet 121 may be such that outlets 121 each having a shape like a quarter of a ring are provided around the outer periphery of the circular inlet 111, as shown in FIG. 6B . Alternatively, the shape and arrangement of the inlet 111 and the outlet 121 may be such that elliptical outlets 121 are provided at positions corresponding to each side of the hexagonal inlet 111, as shown in FIG. 6C . Alternatively, the shape and arrangement of the inlet 111 and the outlet 121 may be such that outlets 121 are provided along the outer periphery of each corner of the rectangular inlet 111, as shown in FIG. 6D .

[0045] <Other> The above-described embodiments are merely illustrative of the present invention, and the present invention is not limited to the specific embodiments described above. Various modifications and combinations of the present invention are possible within the scope of the technical concept. For example, the above-described embodiments illustrate a method for manufacturing a valve element by stacking thin films on a semiconductor substrate through a semiconductor manufacturing process, but the valve element according to the present invention may be manufactured by other methods.

[0046] <Appendix 1> A valve element (1) for controlling the flow of a fluid, a first movable electrode portion (11) having a fluid inlet (111) through which the fluid flows; a second movable electrode portion (12) having an outlet (121) through which the fluid is discharged, the second movable electrode portion (12) being disposed on one surface side of the first movable electrode portion so as to cover the fluid inlet port and spaced apart from the first movable electrode portion; a spacer portion (14) that ensures the gap between the first movable electrode portion and the second movable electrode portion; a frame portion (13) that forms a back chamber (131) that communicates with the fluid inlet on the other surface side of the first movable electrode portion and supports the first movable electrode portion, a voltage is applied to the first movable electrode portion and the second movable electrode portion, and an electrostatic attraction is generated between the first movable electrode portion and the second movable electrode portion, thereby attracting the first movable electrode portion and the second movable electrode portion to seal the fluid inlet port; A valve element characterized by: [Explanation of symbols]

[0047] 1. Valve element 11...First movable electrode part 12...Second movable electrode part 13 Frame section 14 Spacer part 15...Hollow part 110...first movable electrode 111··· entrance 112, 122....insulating film 113, 123... Electrode pads 120...Second movable electrode 121...Discharge port

Claims

1. A valve element for controlling the flow of a fluid, comprising: a first movable electrode portion having a fluid inlet through which the fluid flows; a second movable electrode portion having an outlet through which the fluid is discharged, the second movable electrode portion being disposed on one surface side of the first movable electrode portion so as to cover the fluid inlet port and spaced apart from the first movable electrode portion; a spacer portion that ensures the gap between the first movable electrode portion and the second movable electrode portion; a frame portion that forms a back chamber that communicates with the fluid inlet on the other surface side of the first movable electrode portion and supports the first movable electrode portion, a voltage is applied to the first movable electrode portion and the second movable electrode portion, and an electrostatic attraction is generated between the first movable electrode portion and the second movable electrode portion, thereby attracting the first movable electrode portion and the second movable electrode portion to seal the fluid inlet port; A valve element characterized by:

2. a plurality of sets of the fluid inlet and the outlet corresponding to the fluid inlet; 2. The valve element according to claim 1, characterized in that it comprises:

3. The fluid inlets and the corresponding pairs of outlets are arranged in an array.

3. A valve element according to claim 2, characterized in that it is

4. 1. A method for manufacturing a valve element for controlling fluid flow, comprising: a first electrode forming step of forming a first movable electrode film on a semiconductor substrate, the first movable electrode film having a first movable electrode and a fluid inlet through which the fluid flows; a sacrificial layer film forming step of forming a sacrificial layer film on the first movable electrode film and the semiconductor substrate using an insulating material; a second electrode film forming step of forming a second movable electrode film on the sacrificial layer film, the second movable electrode film having a second movable electrode and an outlet through which the fluid is discharged; a connection electrode forming step of forming a first connection electrode connected to the first movable electrode and a second connection electrode connected to the second movable electrode; a back chamber forming step of forming a back chamber in the semiconductor substrate; a sacrificial layer film etching step of etching the sacrificial layer film while leaving a spacer portion that ensures a gap between the first movable electrode film and the second movable electrode film, A method for manufacturing a valve element comprising the steps of:

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